The antisera for the production of nephrotoxic and chronic autologous immune complex nephritides in rats have been prepared. The KFAb in the nephrotoxic serum has been quantitated. Sufficient quantity of the antisera has been prepared and frozen for use over the next two years. The glomerular hemodynamics have been studied in the early autologous phase of nephrotoxic nephritis in 20 Wistar rats with the collaboration of Doctor Barry Brenner and members of his laboratory in San Francisco. Glomerular deposits of immunoglobulins and glomerular injury was demonstrated by light, immunofluorescence, and electron microscopy. Mild proteinuria was usual present. Despite these signs of injury, whole kidney and single nephron GFR were normal. It was shown that the ultrafiltration coefficient (Kf) of the glomerular capillaries was severely reduced, presumably as a consequence of 1) closing of capillary loops by the proliferative process and 2) by thickening of the capillary walls as a consequence of immunoglobulin deposition. Single nephron GFR was maintained apparently by a reduction in efferent arteriolar resistance, an increase in glomerular plasma flow and an elevated glomerular capillary pressure (i.e., glomerular capillary pressure was 50-60 compared to 40-50 for the controls).